Rider advocates, union workers and supporters from the private sector said Sarles must act quickly on multiple issues - improving customer service, addressing employee concerns and communicating his goals for Metro's future to the public.

Metro union head Jackie Jeter said Sarles faces "a lack of trust in WMATA's ability to restore safety to the system. To regain trust and turn the system around, management - from Sarles all the way down - needs to listen to workers and consider their recommendations."

Others said Sarles must spend more time explaining to the public the competing pressures on Metro as he struggles to overhaul the system.

"His honeymoon will be only a few more months," said Jim Dinegar, president of the Greater Washington Board of Trade. "He will be accountable now. It's on his watch."

As Metro's interim chief, Sarles won over Metro advocates in Congress and local jurisdictions as well as the Metro board, which unanimously voted to give him the job.

Sen. Barbara A. Mikulski (D-Md.), a critic of what she has called negligent safety practices under former Metro chief John Catoe, this week lauded Sarles for having "a commitment to creating the culture of safety we need at Metro." Sarles has "personal integrity, commitment to mission and the skills and experience to operationalize what needs to be done," she said.

Sarles said he offered to stay on in December with the encouragement of Metro staff and local officials. He signed a three-year contract that will pay him $350,000 a year, tackling an assignment some board members joked that he was crazy to accept.

One of his first tasks is filling key vacancies on Metro's staff, including a deputy general manager and some top engineering jobs. Sarles to date has been "constrained" in hiring and firing people in senior positions, said Mortimer Downey, who represents the federal government on the board. Sarles's status as the interim chief has made it difficult for him to attract talented and skilled staff, Downey said.

On Thursday, Sarles pledged to find "the best and brightest" professionals to work for Metro. He said Dave Kubicek, the acting deputy, would be a candidate for deputy general manager. Sarles also said he would work to fill holes in Metro's workforce, particularly a shortage of bus drivers and train operators.

Customer relations should be another priority for Sarles, several rider advocates said.